This is a Shared Instrumentation Grant Application for a new 120kV basic transmission electron microscope (TEM) to be used at the Academic Health Center of the University of Minnesota. The primary purposes of this request are to replace obsolete TEMs, consolidate the use of these instruments, and reinvigorate the science of biological electron microscopy in the University, the State of Minnesota, and the region. The acquisition of this basic instrument is critical in revitalizing electron microscopy as an essential component of structural biology at the university and in maintaining a first-class research enterprise. Six proposed users of the TEM are investigators in the School of Dentistry, and four are faculty members in the School of Medicine. Five users are members of the Institute for Molecular Virology. The proposed projects (by investigator) will use the TEM to 1) determine the structure and molecular mechanisms of assembly of bacteriophage X29 of Bacillus subtilis, a model for assembly of animal viruses and a means to identify targets for antiviral agents;2) determine the relationship between structure and function in kidneys from patients with diabetes and other diseases;3) study the structure and assembly of Eukaryotic cilia and flagella that serve vital sensory and motile functions;4) study localization of calprotectin in keratinocytes, transmucosal transfer of HIV-1, microbial invasion of keratinocytes, and adhesin expression in biofilm formation;5) determine the mechanisms of HIV-1 variation and particle release;6) study the regulatory particle of the proteasome;and 7) determine the tracking of mucosal T cells to commensal microbes;8) study the Alphavirus membrane fusion mechanism.